Ball mill with feed and discharge means at each opposite end



MARTIN BALL. MILL WITH FEED AND DISCHARGE Dec. 29, 1953 MEANS AT EACH OPPOSITE END 2 Sheets-Sheet 1 Filed June 19, 1951 INVENTOR.

I JOHN B- MART/IV ATTORNEY 1953 J. B. MARTIN 2,664,248

BALL MILL WITH FEED AND DISCHARGE MEANS AT EACH OPPOSITE END Filed June 19, 1951 2 Sheets-Sheet 2 INVENTOR.

JOHN B- MART/N YBYWM.

ATTORNEY Patented Dec. 29, 1953 attain 'BALL MILL WITH FEED AND DISCHARGE .MEANS AT EACHiOPPOSITE END John B. Martin, San Franciscm'Calif.

Application June 19, 1951,: Serial=No.=232-,-327

- 6 .Claims.

This invention relates to improvements in ball mills with feed and discharge means at opposite ends and more particularly relates to means for simultaneously feeding ore aggregate :and :discharging ground ore at each ofthe opposite ends of the mill.

' The invention of this application'has'reference in certain mechanical respects to my co-pending application for a ball "mill. Serial No. 790,509,

now Patent No.'2,'5'60,'972 filed December 9, 1947 insofar as the grinding drum portiontof the mill is concerned.

The improvementof thisiinvention is in'the feed and dischargemeans in ball mills, which comprises an axially disposedtubular helical conveyor feed member 'at'each opposite-end ofthe rotatable mill drum,"asifting'screen in each end wall of the mill drum circumferentially ofthetubular feed member and a tubular'helical conveyor discharge member circumferentially enclosing each tubular feed member and spaced therefrom,

;feed and discharge capacity ofa'ball mill of the type "of my said previous application, and to deposit the feed ore aggregaterelatively close to the dischargeorifices for the comminuted ore, Fso that theore aggregate as it is fed into'the m'ill and churned by the balls therein will maintain the comm nuted 'orei'agita-ted in proximity to discharge :screens for such comminuted ore and thereby facilitate sifting "andtdischarge: more :rapidly of the pulverized ores through the screens.

A further object of the invention-is to provide simultaneously operative feed means and discharge means at each end of a ball-mill continually intermittently operative by the rotation .of the drum, and to increase the grinding capacity of the'mill 'inp'r'oximity'to the reception of theorewithinthe grinding compartment of the mill.

One form in which the invention 'may' be exemplified'isdescribed herein and illustrated in "the accompanying drawing, in' whi'cht spaces between the bays.

Fig. 2 is .a vertical ltransverse section on line .2.2 of :Fig. "1, partly brolr'en away.

LFig. l3ris av fragmentary vertical transverse secvtionon line 33=of Fig. 1.

Fig. 4 is.a fragmentary section .online 4-4 i of Fig. .5.

Fig.-5 isa section on line 5-5 ofFig. 1.

Fig. 6 is a-fragmentary front elevation of longitudinal opening of a bay member axially trans- 'verselyof the drum of the-mill, the latter being shown on lines ii-'6 of Fig. :1.

Referring to the drawing in which-like refer- .ence characters indicate correspondingv parts. in the several views, I'll indicates generally therotatable drum' portion of the ball mill which is -mounted for rotationpn a horizontal axis and which-may be the standard conventionaldrum without appurtenant-changes, ormay have any suitable particulars of detailed structures modifled from thestandard conventional i drum to facilitate operation of the novel feed and-discharge-means and-thesifting screen means'associatedtherewith, and suchspecial features of *the-rotary-drum-maybe especially adapted to function with such feed and discharge means. It is-preferred that thedrum'portion of a-mill be of the --general' typedisclosed in my said copending application No. 790,509 with reference to which the drum of'the present inventionmay (be briefly described as having circumferentially spaced elongated-bays H transversely between the end walls of the drum and extending radially'outvvardlyfrom the outer circumference ofzthe central hollow portion of the drum. The bays are inclined 'rearwardly relative to the direction :of rotation ofthe drum and have onerside open- 'inginto'the' drum portion. 7

The drum wall l2 betweenthe opening-of-the bays provides the circumference of the hollow adrumxportio'n of 'the'mill, said'walls being sup ported by 'tiebolts 13 within an outer circumfenentialcasing I Lthe .tie bolts It being inthe Any suitable wear resisting-liners 15 may be providedas inner facing'forathe walls of the drum "and bays, prefer ably-in replaceable sections as indicated in "the drawing.

Rotation of the millmaybe byany wellknown :metms such as the driven gea'r B meshing with :drive "pinion 1 ['1.

Each of" the' end'walls of the drumcomprises 'a"perforated circular disc plate sifting screenlt preferably of diameter of the central portion of the drum exclusive of the bays ll, whereby i.Fig.1.is"a*central verticalsectiondon'gitudinal- -1nilled material maybe dis'charged 'adjacent the circumferencepfsaid drum portion, the openings or perforations 5 8a in the screen preferably being elongated in direction parallel to the circ mference of the reen d sc p ate as best sh wn in Fig. 2. The s ft n s reen plates are coaxial with the mill and each plate has a cent l o in l9 in wh h is fixedly mounted, as by coll r and bolts 2%. one open end of a rotat b e t b lar helical conveyor feed mem er 2! a n th ein throughout its len th a helical r b 2 the tch of the r b bein in d re t on t ards the drum from the o en receiving throat 23 at its opposite or free end.

Mean are provided at the free op n end of each h lical feed on'nv voi" to c t nually. automat c llv and interm ttent surmlv ore a regate thereto. c p n a rotary honner M which is mounted at the fr n o a f the helical feed convev rs and rotate therewith. each such hop er Cflh'inriSlllQ, a generally c rcular chamber member which is a re ervo r for ore g re ate to be fed to the sp r l conveyor. The rotary ho per reservoir chamber has a removable outer planar face 21m having an axial opening 25 centrally thereof th u h wh h a sup of ore a gre ate ma be fed. an havin an axial onening at its inn r rear p anar wall communic ting with the helical conveyor 25 throu h receiving throat 2E. Inte nally each r tary feed hopper is provided with a sub tantially r dial fin or blade 2'? secured at its out r end to the inner face of the circumferential wall of the h per as at 27c and extendin therefrom to a point beyond the axis of the feed opening 26 where it is secured at its said nner en to the rear planar wall of the hopper as at 28. the last mentioned or radially inner end of the blade being curved around the edge of the opening 26 as at 29. In transverse cross ection throu h its body the blade is at an acute an le to the inner rear wall of the ho per so that it provi es therewith a substantially V-shaped an le forming a groove, which, upon rotat on of the blade. picks up ore at a downward position and feeds it by gravity through opening 26 upon rotation to an upward position. Thus the supplying of ore aggregate to the helical feed conveyor is automatic and continually intermittent.

Coaxially with and crcumferentially of and spaced from each of the helical feed conveyors at opposite ends of the mill is a tubular discharge conveyor 3? having a helical rib is! therein, pitched oppo itely relativelv to the pitch of the rib of the feed conveyor. though the incl ne of pitch of rib in the discharge conveyor may be less than in the feed conveyor, due to its greater conveying surface. At its inner end which is securely connected to the end wall of the drum, the di charge conveyor communicates with the drum through the openings 18a of the adjacent screen 53, for wh ch purpose the connected end of the conveyor is flared radially outwardly to substantially eoual the diameter of the screen and drum portion exclusive of the bays, as at 3M to encompass and communicate with a screen of larger diameter than is necessary for the tubula r helical portion of the conveyor. At its opposite or open end the discharge conveyor may be provided with a d scharge bell 32 from which the discharged comminuted ore may be delivered into any suitable receiving bin or tray (not shown). One or more spiders 33 support the feed conveyor and discharge conveyor in relatively spaced relation.

Since the feed conveyors at the opposite ends of the mill are to convey ore aggregate into the drum and the discharge conveyors at said opposite ends convey ground ore material away from the drum, it is obvious that the respective opposite feed and discharge conveyors will have helical ribs oppositely pitched relatively.

It is also to be observed that due to the fixed connect on of the rotatable drum and bays, the sifting screen and the conveyors, the rotation thereof is in unison.

Any suitable means may be provided for supporting the mill rotatively and as herein exemplified comprises tracks 3 adjacent opposite ends of the mill, preferably mounted circumferentally of the discharge conveyors 3 and riding upon the usual relatively spaced rollers 35.

With reference to special structural adaptation of the rotary drum and bays to cooperate with the combined feed and discharge means at each of the opposite ends of the drum, it is to be observed that the greater percent of the ore aggregate in the drum at any one time will be most nearly adjacent the feed inlets, though it will also be spread across the drum in lesser degree toward the center, as indicated by stipling in Fig. 1. The areas adjacent the screens also should be cleared of comminuted ore as rapidly as the ore becomes sufiiciently ground, so that the ground ore near to the screen will not obstruct movement of ground ore from the central portion of the mill towards such screen, and also in order that accumulated ground ore will not act as a shock-absorbing pad to the impact of the cascading and mulling of the balls in the mill. Therefore it is preferred that provision be made for a differential of cascading balls adjacent the feed inlets at the opposite ends of the mill. Since the balls in the lower portion of the drum will, by mulling, seek a substantially uniform depth level, the differential is provided by structurally designing the bays so that the balls lifted by the bays are arranged in the bays with a greater portion of the balls at the opposite end portions of the bays where, when they are thrown or cascaded from the bays, the greater quantity of the balls will impact upon the balls and ore adjacent the opposite end of the drum adjacent the inlet of the feed means. A simple rugged structure to accomplish this result is provided by upwardly crowning the transverse width of the follower wall 3'6 of the bays at its longitudinal central portion as at El so that the width of opening and the volume capacity of the bays is greater at the opposite end portions than at the central portion thereof, providing a pocket at each opposite end of the bays, and whereby, when the follower wall is ascending by rotation of the drum, the follower wall (which is then the bottom wall of the bay) will incline downwardly or rearwardly (relative to direction of rotation) from its central portion towards its opposite ends as shown in Fig. 6, and the balls in the bays will thereby roll in greater quantity from the central portion toward the opposite end pockets and thereby increase the quantity of discharge of balls from the bays adjacent the ends of the mill and into the zone of the fed ore adjacent the feed inlets at the opposite ends of the drum. This additional pounding of the greater quantity of ore at said ends of the drum creates a larger quantity of comminuted ore closely adjacent the discharge screens which sift through the screens with facility without the necessity of the ground particles working their way by creeping through a large body of mixed ore and balls from the central-portion of "the drum towards the dischargesscreens.

In operation, ore='aggregate is fed at eachend of the mill-intothehoppers as through the openings 2 5 whereupon it is picked-up montinually intermittently in relatively smallbatohes as the blades 21 rotate and is delivered automatically to the helical feed conveyor 2!, one great ,advantage of this type of feed means being that by merely removing the face plates Ma the size of radialplate 21 may "bechanged'for various types of ore so thatrtheentirexgrinding capacity of the mill may be always employed, that is, for the .lmoreislowly pulverized hard: orea smaller feed blade Zlmay be emp1oyed,,-whereas for a. more quicklypulverized softer orev a. larger ieed blade 2.1 may be-employedand thus by=a comparatively simple and easily effected adjustment theentire grinding capacity of the mill is available for ores of varying degrees of a hardness.

Ore aggregate having been delivered "to the helical feed. conveyorsZl'it is carried. into both :endsof the drumsimultaneously'and there comminuted by pounding and mulling by the balls 38 in the drum, which latter operation is greatly facilitated and expedited if the mill is provided with radiating bays H which carry a portion of the balls beyond normal position of elevation before cascading them to the mass body of ore and balls in the lower portion of the drum. The two bodies of ore fed into the opposite ends of the drum are constantly opposing each other and this facilitates and expedites the discharge of comminuted ore which Works its way out through the sifting screens H3, at both the opposite ends of the drum, and is picked up by the helical discharge conveyors and discharged to any suitable bin at the bell end of the discharge conveyors.

If the crowned follower wall is employed in the bays to increase pounding, grinding and discharge at the end portions of the mill, the operation thereof has been set forth in connection with the description of structure of such crowned walls in the bays, but it is to be further noted that such increased pounding by cascading the increased volume of balls adjacent the oppo ite ends of the mill closely to the discharge sifting screens also has the effect of increasing the vibration of the balls and ore closely to the screens and thereby increases the discharge by vibrating the comminuted particles through the screen more rapidly.

Having described the invention, what claimed as new and patentable is:

1. In a ball mill, a rotatable drum for receiving balls and ore aggregate, said drum being mounted for rotation on its horivontal axis, axially longitudinally di posed bays which are substantially the axial width of the drum and extend in oircumferentially spaced relation radially outwardly from the outer circumference of the drum, and inclined rearwardly relative to direction of rotation of the drum, each bay having one of its longitudinal sides opening into the drum, and a feed means and-a discharge means mounted at each of the opposite ends of the drum, and a sifting screen at each opposite end of the drum, the said discharge means at each end of the drum communicating with the drum through the screen.

2. In a ball mill, a rotatable drum for receiving balls and. ore aggregate, said drum being mounted for rotation on its horizontal axis, axially longitudinally disposed bays which are substantially the 'axialwidth'of the drum and extend in circumf'crentially spaced relation radially outwardly from the outer circumference of the drum and inclined rearwardly relative to direction of rotation of the drum, each bay having one of its longitudinalsides opening into the drum, and a coaxial feed and discharge means mounted one within the other at each of the opposite ends of the drum and rotatable therewith, and a sifting screen at'each of the opposite ends or" the drum, the said discharge means at each end of the drum communicating with the drum through the screen.

3. In a ball mill, a rotatable drum for receiving balls and ore aggregate, said drum being mounted for rotation on its horizontal axis, axially longitudinally disposed bays which are substan 'tially the axial width of the drum and extend'in circumferentially spaced relation radially outwardly from the outer circumference of the drum and inclined rearwardly relative to the direction of rotation of the drum, each bay having one of its longitudinal sidesopening into the drum, and a feed and discharge means mounted at each of the opposite ends ofthe drum and rotatable there- With, said feed and discharge means at each end of the drum including a disc plate sifting screen in each end wall of the drum and having a central opening therethrough, a tubular helical feed conveyor having one end communicating with the drum through said central opening, and a tubular helical discharge conveyor circumferentially onclosing and spaced from the feed conveyor and communicating with the drum through the screen.

4. A ball mill having a rotatable drum for receiving balls and ore aggregate, said drum being mounted for rotation on its horizontal axis, axially longitudinally disposed bays which are substantially the axial width of the drum and extend in circumferentially spaced relation radially outwardly from the outer circumference of the drum, the bays having one longitudinal side opening into the drum, each bay having a forward wall and a follower wall, the follower walls of the bays being transversely crowned centrally of the length thereof and inclined from said crowned central portion towards the relatively opposite ends of the bays, the incline bein rearwardly relative to the direction of rotation of the drum, whereby pockets are provided at said opposite ends of the bays, a feed and discharge means mounted at each of the opposite axial ends of the drum and rotatable therewith, and a sifting screen at each opposite end of the drum, the said discharge means at each end of the drum communicating with the drum through the screen.

5. A ball mill having a rotatable drum for receiving balls and ore aggregate, said drum being mounted for rotation on its horizontal axis, axially longitudinally di posed bays which incline rearwardly relative to the direction of rotation of the drum, said bays being relatively s aced circumferentially of the drum and extending radially outwardly from the outer circumference of the drum, each bay having one of its longitudinal sides opening into the drum, the follower walls of the bays being transversely crowned centrally of the length thereof and inclined rearwardly from said crowned central portion relative to direction of rotation of the drum whereby pockets are provided at the opposite ends of the bays, a coaxial feed and discharge means mounted one within the other at each of the opposite ends of the drum and rotatable therewith, and a sifting screen at each of the opposite ends of the drum, each of the feed means communicating with the drum at the drum axis and the discharge means communicating with the drum through the sifting screen.

6. A ball mill having a rotatable drum for receiving balls and ore aggregate, said drum being mounted for rotation on its horizontal axis, axially longitudinally disposed bays relatively spaced at the outer circumference of the drum, said bays extending radially outwardly from the outer circumference of the drum, each bay having one of its longitudinal sides opening into the drum, said bays being inclined rearwardly relative to the direction of rotation of the drum and having a forward wall and a follower wall, the follower walls of the bays being transversely crowned centrally of the length thereof and inclined rearwardly relative to said direction of rotation from said crowned central portion towards the opposite ends of the bays providing pockets at the opposite ends of the bays into which balls may roll from the crowned central portion, a feed and discharge means mounted at each of the opposite ends of the drum and rotatable therewith, said feed and discharge means at each end of the drum comprising a sifting screen in the end wall of the drum having a central opening therethrough, a tubular helical feed conveyor having one end communicating with the drum through said central opening, and a tubular helical discharge conveyor circumferentially enclosing and spaced from the feed conveyor and communicating with the drum through the screen.

JOHN B. MARTIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 953,092 Kennedy Mar. 29, 1910 1,275,184 Fairchild Aug. 6, 1918 1,553,613 I-Iolthofi Sept. 15, 1925 1,690,494 Marcy Nov. 6, 1928 2,560,972 Martin July 1'7, 1951 FOREIGN PATENTS Number Country Date 6,464 Great Britain July 21, 1910 205,760 Great Britain Oct. 25, 1923 

